Communication networks are used to transport a variety of signals such as voice, video, data transmission, and the like. Traditional communication networks use copper wires in cables for transporting information and data. However, copper cables have drawbacks because they are large, heavy, and can only transmit a relatively limited amount of data. Consequently, optical waveguide cables replaced most of the copper cables in long-haul communication network links, thereby providing greater bandwidth capacity for long-haul links. However, most communication networks use copper cables for distribution and/or drop links on the subscriber side of the central office. In other words, subscribers have a limited amount of available bandwidth due to the constraints of copper cables in the communication network. Stated another way, the copper cables are a bottleneck that inhibit the subscriber from utilizing the relatively high-bandwidth capacity of the long-hauls links.
As optical waveguides are deployed deeper into communication networks, subscribers will have access to increased bandwidth. But there are certain obstacles that make it challenging and/or expensive to route optical waveguides/optical cables deeper into the communication network, i.e., closer to the subscriber. For instance, laying the last mile of fiber to the subscriber requires a low-cost fiber optic cable that is craft-friendly for installation, connectorization, slack storage, and versitilty Moreover, the reliability and robustness of the fiber optic cable must withstand the rigors of an outdoor environment.
FIG. 1 schematically illustrates two different methods for routing fiber optic cables to a premises 19. Specifically, FIG. 1 shows a first method of routing a figure-eight cable 10 to premises 19 in an aerial application and a second method using a cable 10′ routed to premises 19 in a buried application. In aerial applications, cable 10 may be a figure-eight cable having a first end 10a that is attached at a first interface device 12 located on pole 11 and a second end 10b that is merely a portion of cable 10 that is routed to an interface device 14 at premises 19. Specifically, figure-eight cables have a messenger section and a carrier section that can be split apart near premises 19. More specifically, messenger section can include a conductive strength member for carrying the tensile load of cable 10 and is terminated and attached with a clamp positioned at a tie point 19a of premises 19. Carrier section of figure-eight cable 10 includes one or more optical fibers therein and is routed along a side of premises 19 to interface device 14. In buried applications, the first and second ends of cable 10′ are respectively routed to pedestal 18 and connected to interface device 16 and routed and connected to interface device 14.
One such figure-eight drop cable is disclosed in U.S. Pat. No. 6,546,175 and preferably has a carrier section that does not include strength members. The carrier section of this cable is flexible when split from the messenger section for slack storage; however, the carrier section does not have anti-buckling members so the polymer materials of the carrier section may shrink with environmental temperature changes, thereby causing elevated levels of optical attenuation. Another figure-eight drop cable is disclosed in U.S. Pat. No. 6,356,690 having a carrier section with strength members that provide anti-bucking to the carrier section. Strength members may be a material such as steel that aids in inhibiting the shrinkage of the carrier section; however, the steel strength members make the carrier section relatively stiff, thereby inhibiting slack storage. In other words, the strength members increase the bending radius of the carrier section and when coiled the strength members act like a coiled spring that wants to unwind. Moreover, the potential for elevated attenuation still exists.
Cables have used other strength members such as conventional fiberglass yarns, but they provide less anti-buckling strength than rigid strength members. U.S. Pat. No. 6,487,347 discloses an optical cable using conventional fiberglass yarns; however, the cable requires a relatively large number of flexible strength members for adequate performance. The use of a relatively large number of conventional fiberglass yarns increases the manufacturing complexity, increases the cost of the cable, and makes the cable relatively stiff. Thus, this cable does not meet all of the requirements for a drop cable that is suitable for routing optical waveguides to the subscriber.